Pulse width modulation of a signal involves the modulation of the duty cycle (D) of the signal in order to carry data in a “digital form”, where the duty cycle is the fraction of time that a system is in an “active” state. For example, in an ideal pulse train (having rectangular pulses), the duty cycle is the pulse duration divided by the pulse period, and represents the data value carried by the signal. In some situations it may be preferable to carry data using a PWM signal in this way.
However, in other situations it may be preferable to express the data in an analog voltage signal by an analog voltage level of the signal. Converters are known which convert PWM signals into analog voltage signals. The converters may include an amplifier and other components. The accuracy of a converted signal may be adversely affected by the offset of the amplifier and any components mismatch in the converter.